Some are born with a conscience. Others are not. And that conscience is pretty circumscribed, both by Nature and nurture.We are always dealing with extenuating circumstances, but unless damaged in some way, we come equipped with an in-born conscience. Kind of like a compass leaning toward what is right. So, a conscience can be trained or guided to distinguish between right and wrong or vice versa.
We have the brains of hunter-gatherer, plains apes. They're wired for in-group altruism and out-group competition.
Extending moral consideration to non-tribe members is not part of our inborn survival strategy. Such altruism would have been dysfunctional for 99% of our history. It has to be learned and, once enculturated, it's a very thin veneer, easily stripped away.